Families face a growing burden of care for elderly and disabled relatives and most people will have to pay for their own support services in old age as the state's role shrinks, the government's care watchdog will warn today.

A fundamental shift in responsibility is taking place as councils respond to spiralling demand by concentrating resources on fewer people with greater needs, the Commission for Social Care Inspection will say in a report.

Dame Denise Platt, who chairs the commission, is expected to say that older people in much of England can anticipate no help from the state until their needs are judged "critical". Her report will urge fresh thinking on the help given to families in what will be the first high-level recognition of a trend across the country.

Dame Denise will warn that at the moment people without family or friends able or willing to help them, or without the means to buy in care, are being left to cope as best they can.

She will say that responsibility should not be passed over in this way without a proper infrastructure in place to enable people to find alternative sources of care and to offer greater support for family carers. She will call on ministers to acknowledge the realities and to negotiate a new "pact" between state and individual.

The crisis in care services reflects the growing longevity of disabled people, often with high support needs, but mainly the swelling elderly population. The number of people aged 65 and over is projected to increase by more than 80% to almost 17 million in the first half of this century; the number of those 85 and over is expected to double to more than 1.8 million by 2028.

The impact of this on the care system was highlighted last year by an unofficial report by a team led by Sir Derek Wanless, who calculated that spending on personal care for older people would have to treble to £30bn a year over the next two decades to maintain the status quo. Critics believe ministers have filed the Wanless recommendations for reform of care funding in the "too difficult" basket and hopes are not high of a significant boost for social care in the forthcoming three-year spending review. But developments on the ground have brought issues to a head.

While debate about Wanless has focused on residential care - where more than 30% of people are now paying some or all their fees of £400 a week in care homes and £600 in nursing homes - a growing outcry has been prompted by restrictions placed by councils on services for people remaining in their own homes.

Two in three English councils now limit home care, such as assistance with dressing, washing and cooking, to people with needs assessed as "critical" or "substantial". Most councils expect to tighten these criteria further this year. According to the Local Government Association, help currently provided to up to 370,000 people with assessed lower-level needs will disappear altogether by 2009. In a joint letter published in the Guardian shortly before Christmas, leaders of 45 councils warned that "services for the elderly are now teetering on the brink. The present situation is unsustainable."

What particularly worries the care inspectorate is that many people are unaware of what is happening and have unrealistic expectations. A recent survey for the LGA found a third of adults thought they would automatically get free home care in their old age and only 10% thought they would have to pay for it entirely from their own pocket.

The inspectorate will today say councils are acting sensibly in rationing support, and are getting better at accurately assessing needs. But it will also say that many councils are doing little to help those who have to find their own care, at average charges of more than £10 an hour. This echoes a report published this week by care advice charity Counsel and Care, which warned of a widening "care gap" between people's needs and available services and called for measures including appointment of independent care advisers in every community and creation of a national care advice service.